Tuesday, 26 October 2010

First there was standard time

For millennia, people have measured time based on the position of the sun; it was noon when the sun was highest in the sky. Sundials were used well into the Middle Ages, at which time mechanical clocks began to appear. Cities would set their town clock by measuring the position of the sun, but every city would be on a slightly different time. Britain was the first country to set the time throughout a region to one standard time. The railways cared most about the inconsistencies of local mean time, and they forced a uniform time on the country. By 1855, the vast majority of public clocks in Britain were set to GMT.

So why change the clocks in the summer? It's over 100 years since British Summer Time was first proposed by William Willett ( an enthusiatic 'lark') who was incensed at the 'waste' of useful daylight first thing in the morning, during summer. Britain first adopted a revised version of William Willett's Daylight Saving Time scheme in 1916, reasoning that any system that could save fuel and money was worth trying. Now, after a century of daylight saving, we still cannot agree on whether it is a good thing or not.

The return to GMT on Sunday may help us get back in tune with the natural rhythm of night and day. In a study of more than 50,000 people, researchers found that the sleep pattern on free days (i.e. when someone doesn’t have to go to work) follows the natural progression of dawn during winter time, but not during the summer, when daylight saving time is imposed.

These findings were confirmed by a smaller study of 50 volunteers. In these people, the timing of sleep and activity adjusted well to the return to standard time (in the winter), but not so well to the change to daylight saving time in the summer months. This problem of adjusting was particularly pronounced in people who were 'late' chronotypes, i.e. the 'owls' or 'evening' people, compared with those who had the 'early' chronotype – the 'larks'.